Article 50, which triggers Britain's exit from the EU, can be reversed, according to the man who wrote it.

Lord Kerr of Kinlochard, a former EU ambassador, said Brexit could be reversed right up to the last minute, despite Theresa May today announcing a withdrawal date and time would be on the bill going before Parliament next week.

The prime minister said the EU Withdrawal Bill would be amended to formally commit to Brexit at 11pm GMT on Friday, March 29 2019.

But Lord Kerr said Brexiteers were claiming Brexit was irreversible and thereby misleading the public.

Writing for The Times' Red Box blog, he said: "Mrs May’s March letter [triggering Article 50] can be withdrawn.

"If you buy a top of the range car, and it turns out to be an old banger with smoke pouring out of the bonnet, you have the right to take it back to the dealers.

"If a restaurant serves you scampi and chips instead of a steak, it is your right in this country to return it to the kitchen.

"If the form of Brexit sold to the British people does not emerge at the end of the negotiations, voters have the right to change their minds about whether they want to go through with it."

Mrs May's Article 50 letter was only a notification of the UK’s “intention” to withdraw from the EU, Lord Kerr said, and was not binding.

"If the Lisbon Treaty had intended that reporting a plan to leave the EU meant that one must inevitably leave, it would say so," he said. "But it does not."

Writing in the Daily Telegraph today, Mrs May said the decision to put the specific date and time of withdrawal "on the front page" of the Brexit bill showed her government was determined to deliver on the referendum vote.

"It will be there in black and white on the front page of this historic piece of legislation: the United Kingdom will be leaving the EU on March 29, 2019 at 11pm GMT."

She said the government would listen to MPs if they had ideas for improving the bill, but warned against any attempts to halt Brexit.

"We will not tolerate attempts from any quarter to use the process of amendments to this Bill as a mechanism to try to block the democratic wishes of the British people by attempting to slow down or stop our departure from the European Union," she said.

But Lord Kerr said: "Simply, there is no doubt in my mind that our Article 50 letter can be withdrawn without political or legal difficulty, and without economic cost.

"Once we are out, the road back would be much longer and more difficult.

"And if Parliament and the people seek another say on this immense economic and constitutional change, it would not be difficult to gain more time to put the question back to them."

It comes as the Brexit secretary, David Davis, and the EU’s chief negotiator, Michel Barnier, prepare to meet in Brussels on the second day of the latest round of talks before a summit of European leaders next month.

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